Various arrangements for providing mechanical force to perform operations with downhole tools for accomplishing certain downhole tasks are known. For example, piston assemblies for converting pumped fluid pressure to linear mechanical force in a downhole tool are used in setting tools for packers, plugs, liner top hangers, casing patches, etc., as well as downhole tools such as straddle packers, tubing perforators and the like. Such piston assemblies employ a plurality of pistons connected in series to an inner or outer mandrel of a downhole tool to increase the linear force that can be generated from a given fluid pressure of fluid pumped down through a work string to the downhole tool. An example of one such piston assembly can be found in U.S. Pat. No. 8,336,615 which issued on Dec. 25, 2012. While such piston assemblies have proven useful, it is at times desirable to utilize pumped fluid pressure for a different or additional purpose. A means of downhole force multiplication that does not reply on pumped fluid pressure is therefore desirable. One such alternative force multiplier, which operates on a pull-up force applied from the surface to a work string connected to a modular force multiplier, is described in Applicant's co-pending U.S. patent application Ser. No. 15/980,992 filed May 16, 2018, the entire specification of which is incorporated herein by reference.
However, there remains a need for a modular force multiplier for downhole tools that operates on a push-down force applied from the surface to a work string connected to the modular force multiplier.